Casein glycomacropeptide pH-driven self-assembly and gelation upon heating

Casein glycomacropeptide (CMP) found in cheese whey is a C-terminal hydrophilic glycopeptide released from κ-casein by the action of chymosin during cheese making. In a previous work a self-assembly model for CMP at room temperature was proposed, involving a first step of hydrophobic assembly followed by a second step of electrostatic interactions which occurs below pH 4.5. The objective of the present work was to study, by dynamic light scattering (DLS), the effect of heating (35–85 °C) on the pH-driven CMP self-assembly and its impact on the dynamics of CMP gelation. The concentration of CMP was 3% w/w for DLS and 12% w/w for rheological measurements. The solutions at pH 4.5 and 6.5 did not show any change in the particle size distributions upon heating. In contrast the solutions at pH lower than 4.5 that showed electrostatic self-assembly at room temperature were affected by heating. The mean diameter of assembled CMP increased by decreasing pH. For all solutions with pH lower than 4.5, the particle size did not change on cooling, suggesting that the assembled CMP forms formed during heating were stable. The gel point determined as G′–G″ crossover, occurred in all systems at 70 °C, but at different times. The rate of self-assembly determined by DLS as well as the rate of gelation increased with increasing temperature and decreasing pH from 4 to 2. Increasing temperature and decreasing pH, the first step of CMP self-assembly by hydrophobic interactions is speed out. All the self-assembled structures and the gels formed at different temperatures were pH-reversible but did not revert to the initial size (monomer) but to associated forms that correspond mainly to CMP dimers.     

Synthesis of “walnut-like” BiOCl/Br solid solution photocatalyst by electrostatic self-assembly method

In this paper, under the control strategy of surface charge of BiOCl photocatalyst and the electrostatic adsorption of anions and cations in potassium bromide (KBr) and polyvinylpyrrolidone (PVP), the self-assembly of “walnut-like” BiOCl/Br solid solution nanophotocatalyst at a lower temperature water bath was proposed for the first time. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive system (EDS), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), UV-Vis, photoluminescence spectroscopy (PL) and Mott-Schottky curve, transient photocurrent densities, and electrochemical impedance spectroscopy (EIS) were used to analyze the properties of materials, including its morphology, element distribution and chemical states, specific surface area, electrochemical property, and photogenic charge transfer. Based on the degradation performance of RhB dye wastewater and phenol in visible and ultraviolet light, and the band structure of BiOCl/Br solid solution, the reason for the improved photocatalytic activity was deeply discussed, and the possible degradation mechanism was also put forward. The above results show that Br⁻ can be inserted into the crystal lattice of BiOCl under the effect of electrostatic adsorption to form solid solution by the interaction between atomic orbitals, which not only reduces the bandgap width but also improves the separation and mobility of photogenic electrons and holes, causing the absorbed light to shift red to the visible region. In addition, when the n_Br⁻/n_Cl⁻ = 0.67, “walnut-like” BiOCl/Br solid solution was formed, and this kind of special core-shell structure not only can increase the specific surface area, increase the number of active sites, but also can make the light reflect and refract many times in the cavity and further increase the utilization rate of light energy, and then the best photocatalytic activity was achieved. This study provides an new method to enhance the photocatalytic performance of BiOCl and be conducive to the development of modern material science.     

Solving Nafion poisoning of ORR catalysts with an accessible layer: designing a nanostructured core-shell Pt/C catalyst via a one-step self-assembly for PEMFC

A core-shell Pt/C@NCL300 catalyst with an accessible layer was designed to recover lost ORR activity and was constructed via a one-step self-assembly process in this paper. A thin porous layer derived from Nafion was first formed on the surface of Pt/C catalyst to create a shell. This first coating successfully separated the Nafion and Pt particles in the catalysts and reducing the negative impact of Nafion on ORR activity and enhancing the fuel cell performance. The newly fabricated Pt/C@NCL300 catalyst exhibited much higher specific activity than the original Pt/C catalyst in RDE tests under the same conditions and were comparable to the activity of Pt/C electrode without Nafion poisoning. Moreover, the fuel cell with Pt/C@NCL300 catalyst exhibited a higher power density without an obvious increase in proton transport and O₂ transport resistance compared to that of a Pt/C fuel cell with a low Pt loading. This result indicates that coating the Pt/C catalyst with a layer accessible for oxygen and protons is a promising way to effectively promote Pt-based catalysts that work under normal operating conditions.     

Facile synthesis of C-doped hollow spherical g-C3N4 from supramolecular self-assembly for enhanced photoredox water splitting

A facial, template-free and green strategy was developed to prepare C-doped hollow spherical g-C₃N₄ derived from supramolecular self-assembly of melamine, glucose and cyanuric acid. Especially, the precursors were tightly connected by hydrogen bonds, wherein glucose was served as a source of doped carbon. Spectroscopic and electrochemical analysis confirmed that the endmost nitrogen was replaced by the doped carbon to combine two melon parts, leading to the possible existence of the delocalized big π bonds in the system. Moreover, the GCN-x not only maintained the excellent properties of the hollow sphere, such as high surface area, moderate porosity and short charges diffusion distance, but also overcame the drawbacks of low visible light response and high electron-holes recombination rate from bulk g-C₃N₄. Thereby, the visible light utilization rate and the photogenerated electron-holes separation efficiency of the catalyst were improved. The highest hydrogen yield of 305  μmol h⁻¹ from GCN-0.2 was 28.5 times that of bulk g-C₃N₄. Finally, a possible mechanism underlying the photocatalytic performance of C-doped g-C₃N₄ hollow spheres was proposed tentatively.     

溶胶凝胶-液态熔盐静电自组装复合工艺制备cBN@Al核壳粉体

机械混合的cBN和金属Al粉是制备超硬切削刀具的重要原料,因此能有效提高两者接触面积的金属Al包覆cBN的核壳粉体具有潜在的经济价值。提出了一种先将cBN粉体表面羟基化,再通过溶胶-凝胶法对cBN表面进行硅氧纳米层改性,然后在熔融盐条件下包覆金属Al壳层,最后将核壳产物提纯的工艺路线。在不同条件的热处理和不同热处理时间下制备样品,并通过XRD、DSC、SEM、TEM和N_2等温吸附脱附测试,探讨对包覆的影响因素及其机理。结果表明:基于布朗运动和静电自组装机制形成了多孔结构的包覆层,硅氧桥接层、导电熔融盐环境和热处理时间都对包覆Al壳层有重要影响。热处理2 h可获得平均粒径5.7μm和比表面积10.988 m~2/g且含杂质较少的cBN@Al多孔粉末。该项工作为在惰性无机粉末上涂覆活泼的轻金属壳层提供了新的思路。     

静电层层自组装法整理多巴胺改性涤/棉混纺织物的阻燃性能

为了赋予涤/棉混纺织物良好的阻燃性能,以pH值为5、质量分数为1%壳聚糖溶液和pH值为2、质量分数为1.5%植酸钠溶液,通过静电层层自组装法,对经多巴胺改性后的涤/棉(65/35)混纺织物进行阻燃整理。其中正负离子交替沉积1次记为组装1层,第1层内每次组装15 min,第1层后各次组装时间为5 min,共组装15层。探讨了整理后织物极限氧指数(LOI)、炭长、热重、热释放速率、炭渣形貌等性能。结果表明:多巴胺改性可以提高涤/棉混纺织物的反应性,有利于阻燃整理;整理后织物阻燃性能显著提高,LOI值从未整理时的18.8%提高到28.7%;热分解温度比未整理织物大幅提前,炭渣含量较未整理提高了5.7%;整理后织物点燃时间延长,平均热释放速率(HRR)和峰值热释放速率(PHRR)分别为14.16 k W/m2和51.07 k W/m2,相较未整理涤/棉织物下降了84.62%和78.47%,织物燃烧危险性显著降低。     

木质素调控制备果糖基碳微球及其电化学性能研究

本研究使用果糖作为碳源,木质素磺酸盐协同三嵌段共聚物P123作为模板剂,经过水热碳化法和高温碳化法制备果糖基碳微球材料。探究了木质素磺酸盐对果糖在水热条件下的组装过程及调控机制,并分析果糖基碳微球材料在电化学领域的应用。结果表明,木质素磺酸盐的加入是微球表面形成波纹状突起的决定因素。经高温碳化处理过后得到中空多孔的Yolk-Shell果糖基碳微球材料具有良好的电化学性能,其比表面积为535. 04 m~2/g,孔容为0. 26 cm~3/g;在电流密度为0. 1 A/g时,其比电容为96 F/g,能量密度为3. 16 Wh/kg,功率密度为28. 06 W/kg。     

Illumination-induced properties of highly ordered mesoporous TiO2 layers with controlled crystallinity

The evaporation-induced self-assembly method using a novel diblock (poly(ethylene-co-butylene)-b-poly(ethylene oxide)) copolymer (KLE) provides fully crystalline mesoporous layers of TiO₂ exhibiting high thermal stability up to 700 °C, high photocatalytic activity in the decomposition of methyl stearate and facile transformation into a substantially stable superhydrophilic state by 1 mW/cm² UV-illumination.     

Fabrication and third-order nonlinearity of an ultrathin film containing perylene derivatives

An ultrathin composite film containing cationic tetra-pyridine perylene tetracarboxylic acid diimide (TPP-I) and an anionic tetra-sulfuric perylene tetracarboxylic acid diimide (TSP-Na) has been fabricated by the electrostatic layer-by-layer self-assembly technique. UV/Vis spectra showed a continuous and uniform deposition process of TPP-I/TSP-Na. The film structure was characterized by the small-angle X-ray diffraction measurement and atomic force microscopy image. We investigated the third-order nonlinearity of the ultrathin film sample at 532 nm. The film exhibited strong saturable nonlinear absorption. The nonlinear absorption coefficient and refractive index of the film sample are − 5.0 × 10^− 7 mW^− 1 and − 1.2 × 10^− 14 m²W^− 1, respectively.     

聚六亚甲基双胍盐酸盐在棉织物上的静电自组装及其抗菌性能

 将聚六亚甲基双胍盐酸盐(PHMB)和聚苯乙烯磺酸钠(PSS)通过静电自组装构筑在棉纤维表面,赋予纤维抗菌性能。扫描电镜表明纤维的表面形态发生明显变化,组装后纤维表面粗糙,有沉积物质覆盖。Zeta电位和染色着色深度证实表面电位及K/S值随纤维表面沉积物质不同呈有规律的"层层交替振荡"现象,揭示了纤维表面层层静电自组装的构筑机制。组装后棉织物的抑菌率达到99.51%,显示出优异的抗菌性能,且组装整理后的棉织物耐水洗牢度较好。